1. Field of the Invention
This invention relates generally to sensing systems and, more particularly, to a system that senses fluid type and fluid level in a fuel tank of a motor vehicle so as to provide signals indicative of the type of fuel being used and the vehicle fuel level.
2. Discussion of the Related Art
Conventional motor vehicles have generally utilized steel fuel tanks in the fuel system. However, automotive manufacturers have recently began to convert to plastic or polymer type fuel tanks to achieve weight reduction and cost savings. This change in material also provides a convenant medium in which electromagnetic communications from within the fuel tank to outside the fuel tank may be passed. Yet, existing fuel level indicators still employ mechanical floats and powered sensors that require access through the wall of the fuel tank.
With the increased concerns in hydrocarbon emissions from motor vehicles, there has also recently been an increased emphasis placed upon trying to reduce these hydrocarbon emissions which are generally regulated by governmental concerns. Some of the factors taken into consideration to reduce these hydrocarbon emissions is to reduce or eliminate any vapor leakage of fuel throughout the fuel delivery system. In this regard, any time an access port or bore needs to be formed within a wall of a fuel tank, this is a possible area for vapor and fuel leakage. Therefore, should it be possible to reduce or eliminate the number of input and output ports that must run within a fuel tank, a reduction in fuel vapor and leakage is possible.
What is needed then is a fluid type and fluid level sensing system that provides accurate fluid type and level indications that does not suffer from the above-mentioned disadvantages. This, in turn, will reduce or eliminate the number of ports passing through the wall of a fuel tank, reduce or eliminate hydrocarbon emissions based on fuel vapors leaking through these passageways or ports, provide an accurate and cost effective fluid type and fluid level indicator, and reduce the overall fuel tank assembly cost and complexity. It is, therefore, an object of the present invention to provide such a fluid type and fluid level sensing system for use in a fuel tank of a motor vehicle or for any other type of fluid retaining vessel.
In accordance with the teachings of the present invention, a fluid sensing system for sensing various parameters of fluid in a fluid container is disclosed. This is basically achieved by using a fluid sensor and a fluid receiver which are each positioned remote therefrom and in electromagnetic communication with each other.
In one preferred embodiment, a fluid sensing system for determining a fluid parameter within a fluid container includes a fluid sensor and a fluid receiver. The fluid sensor is positioned at a first location and is operable to sense the fluid parameter. The fluid receiver is positioned at a second location remote from the first location and within proximity to the fluid sensor. The fluid receiver includes an amplifier having a feedback path such that the amplifier is in a waiting non-oscillating mode when the fluid sensor is not electromagnetically coupled to the fluid receiver and in an active oscillating mode when the fluid sensor is electromagnetically coupled to the fluid receiver. This provides a feedback in the feedback path that is one of either a substantially zero feedback and a negative feedback when the amplifier is in the waiting, non-oscillating mode and a feedback in the feedback path that is a positive feedback when the amplifier is in the active oscillating mode.
Use of the present invention provides a fluid sensing system for sensing a fluid parameter within a fluid container. As a result, the aforementioned disadvantages associated with the currently available fluid sensing systems have been substantially reduced or eliminated.